When low sulfur coal containing iron or calcium in insufficient amounts is charged to a Texaco free-flow coal gasifier as feedstock for the production of synthesis gas, reducing gas, or fuel gas, the ash particles produced are characterized by an undesirably high melting or fusion temperature. The partial oxidation of coal slurries is described in coassigned U.S. Pat. No. 3,544,291, which is incorporated herein by reference. The reduction of the oxides of iron, copper, vanadium or barium, and the simultaneous production of carbon monoxide and hydrogen in an oil fired partial oxidation gas generator is described in coassigned U.S. Pat. No. 2,824,792.
When the gasifier is operated in the slagging mode, the temperature in the reaction zone is kept sufficiently high in order to melt the fine ash particles and thereby produce molten slag. In the molten form, slag may be more readily separated from the raw effluent gas stream and from the reaction chamber. In the case of solid carbonaceous fuels having relatively low iron, sulfur and calcium constituents, the gasifier must be operated at temperatures above 2700.degree. F. in order to achieve the desired molten state of the slag. However, such temperatures are undesirable in that they may reduce refractory life. Furthermore, thermal efficiency suffers in that desirable synthesis gas product is burned to generate heat for melting the slag. Some examples of coals having low contents of sulfur, iron, and calcium are Lake Desmet coal and certain Australian coals, e.g., Moura coal and R. W. Miller coal.
It is an object of this invention to provide a novel process for the production of synthesis gas, reducing gas or fuel gas in a slagging-mode free-flow gasifier that operates at lower reaction temperatures than those ordinarily required for the partical oxidation of a solid carbonaceous fuel e.g. coal having a normally high ash melting or fusion temperature. It is also an object of this invention to use the iron sulfide contained in the waste products from coal washing processes to simultaneouly achieve a lowering of the coal ash fusion temperature in coal gasification, and for the environmentally acceptble disposal of coal cleaning waste products. Other objects will be apparent to those skilled in the art.